The invention relates to an X-ray apparatus. The apparatus comprises a part which is movable thereon and a counterweight hydraulically coupled with the moveable part. The counterweight is movable opposite the moveable part. A cylinder system is provided for hydraulically transferring forces.
Such an X-ray apparatus is described in German Pat. No. 1,728,886. In this apparatus, the counterweight is connected to a piston and the moveable part (an X-ray sighting mechanism) is connected with a cylinder. The piston divides the cylinder into two chambers connected through ducts with a fluid pump or the like so that fluid can be pumped from one chamber into the other. As a result, the piston is displaced in the cylinder, and hence the X-ray sighting mechanism is also displaced.
In the rest position (i.e. when no force is exerted on the piston, the X-ray sighting mechanism is held in place by the counterweight. When a force is exerted on the sighting mechanism, the counterweight and the sighting mechanism first move in opposite directions so that only inertia and friction need be overcome. However, as soon as the counterweight has moved over a given distance, the pump is operated so that the X-ray sighting mechanism is displaced by the pump pressure. Since after this operation the counterweight is returned to its initial position, the effort for lifting the X-ray sighting mechanism must be performed by the pump. If the pump or the pump control is defective displacement of the X-ray sighting mechanism is practically impossible.
Another X-ray apparatus is known in which the moveable part can be manually moved by the user German Pat. No. 2,324,699, and U.S. Pat. No. 3,933,251, corresponding thereto.) The part can be moved manually because the counterweight is automatically moved in a sense opposite the X-ray sighting mechanism. The forces are transferred by ropes passed around a number of rollers. The forces required to overcome the friction in the ropes may, when the moveable part is heavy, however, attain unexpectedly high values.